Abstracts
Abstract
Lower Carboniferous ostracode assemblages of marine affinity occur in sediments of the Codroy Group in southwestern Newfoundland and the Windsor Group in central Nova Scotia. Three ostracode assemblages are defined from Nova Scotia and five from Newfoundland. The assemblages are described from biohermal and non-biohermal limestones and fine-grained sihciclastic lithologies. The assemblages can be characterised by their responses to varying degrees of physiological stress, and are dominated by members of the Paraparchitacea, although bairdiaceans, hoDinomorph and kirkbyacean palaeocopids and kloedenellaceans may be locally abundant.
In the Maritimes Basin, the combined effects of tectonism, eustatic fluctuation and a semi-arid climate resulted in palaeoenvironments that were characterised by low temporal and spatial stability. As a consequence, total ostracode species richness relative to individual species abundances was low, and often expressed in the development of low grade communities that were controlled more by physical (allogenic) rather than biological (autigenic) parameters. Under these conditions the eurytopic paraparchitaceans were capable of producing large populations in physically harsh palaeoenvironments, whereas die more stenotopic bairdiaceans and palaeocopes only occurred when conditions were favourable.
RESUME
Les sediments des groupes de Codroy (sud-ouest de Terre-Neuve) et de Windsor (centre de la Nouvelle-Ecosse) renferment des assemblages d'Ostracodes, a affinity marine, du Carbonifere infcrieur. On reconnait trois assemblages en Nouvelle-Ecosse et cinq a Terre-Neuve. Ces assemblages proviennent de calcaires (biohcrmaux ou non) et de lithologies siliciclastiques a grain fin. On peut caracteriser ces assemblages par leurs re'ponses aux divers degree de stress physiologique. On y note lapr&lominance des repr&entants des Paraparchitacea malgre' l'abondance locale des bairdiacls, des pal6ocopid& hollinomorphes et kirkbyaces ainsi que des kloedenellaces.
Dans le Bass in des Maritimes, la conjonction de divers facteurs (tectonisme, fluctuations eustatiques, climat semi-aride) se traduisit par des pal6omilieux caracte>is£s par une stability spatiale et temporelle faible. En consequence, larichesse specifique totale des Ostracodes £tait basse par rapport aux abondances sp&ifiques individuelles et s'exprimait souvent part le developpe-ment de communautes immatures controlees par des parametres plus physiques (allogenes) que biologiques (autogenes). Dans ces conditions, les paraparchitacea eurytopiques pouvaient peupler abondamment les pal&>milieux physiquement exigeants, alors que les bairdiace's et les paleocopes (qui 6taient plus ste'notopiques) n'&aienl presents que dans des biotopes favorables.
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